Methods and systems for processing crude oil

ABSTRACT

Methods and systems for processing crude oil may include adding water to crude oil, for example, in a desalter, to produce hydrocarbon and brine and a rag layer emulsion, which may include hydrocarbon and brine and solids. The emulsion may be modified, including adding one or more of additional hydrocarbon and, a demulsifier, a reverse demulsifier, a coagulant, and a flocculant, for example, in a mixer. The modified emulsion may be directed through a dead-end filter assembly to remove solids.

DISCLOSURE OF THE INVENTION

During some crude oil refinery processes, an emulsion also known as a“rag layer” or “slop” may form. This rag layer may include an emulsioncomprising any one or more of several substances, including, forexample, oil or hydrocarbons, brine, asphaltenes, and/or solids. Thesolids may include small solid particles of metal or grit or othersubstances as well as colloidal particles, and the rag layer may causefouling and corrosion of the refinery system. Accordingly, there is aneed for improved methods and systems for processing crude oil.

In accordance with one aspect of the invention, methods for processingcrude oil may comprise adding water to crude oil to produce hydrocarbonand brine and a rag layer emulsion. The methods may further comprisemodifying the rag layer emulsion, including adding one or more ofadditional hydrocarbon, a demulsifier, a reverse demulsifier, acoagulant, and a flocculant to the emulsion, and directing the modifiedemulsion through a dead-end filter assembly to remove solids. A dead-endfilter assembly is one in which all fluid entering the filter assemblypasses through a permeable or porous filter medium. As the modifiedemulsion passes through the filter medium of the dead-end filterassembly, all or a substantial portion of the solids are removed fromthe modified emulsion.

In accordance with another aspect of the invention, systems forprocessing crude oil may comprise a desalter, a mixer, and a dead-endfilter assembly. The desalter may include one or more inlets forintroducing crude oil and water into the desalter. The crude oil andwater combine within the desalter to produce oil or hydrocarbon andbrine and a rag layer emulsion. The desalter may also include a firstoutlet for discharging at least a portion of the hydrocarbon and one ormore additional outlets for discharging the rag layer emulsion. Themixer, which may be coupled to the desalter, modifies the rag layeremulsion, including mixing the emulsion and one or more of additionalhydrocarbon, a demulsifier, a reverse demulsifier, a coagulant, and aflocculant added to the emulsion. The dead-end filter assembly may becoupled to the mixer to filter solids from the modified emulsion.

Methods and systems embodying the invention provide many advantages. Forexample, methods and systems embodying the invention may advantageouslyreduce or eliminate fouling and/or corrosion in oil refinery systems byremoving solids that would otherwise damage the components of therefinery system. Further, methods and systems of the invention allow therag layer to be effectively and efficiently processed, recovering muchof the rag layer hydrocarbon, including oil, that would otherwise belost if the rag layer were not processed. Accordingly, the methods andsystems of the invention may advantageously increase the reliability,efficiency, and capacity of oil refinery processes.

BRIEF DISCLOSURE OF THE DRAWINGS

FIG. 1 is a representative schematic view, not to scale, of oneembodiment of a system for processing crude oil.

FIG. 2 is a representative schematic view, not to scale, of anotherembodiment of a system for processing crude oil.

FIG. 3 is a representative schematic view, not to scale, of anotherembodiment of a system for processing crude oil.

FIG. 4 is a representative schematic view, not to scale, of anotherembodiment of a system for processing crude oil.

DESCRIPTION OF EMBODIMENTS

Systems and methods for processing crude oil in accordance with theinvention may be configured in a wide variety of ways. One of manydifferent examples of a system 10 for processing crude oil within arefinery system is shown in FIG. 1. Generally, the system 10 maycomprise a desalter 11, a mixer 13, and a dead-end filter assembly 14.In the illustrated embodiment, the system 10 may also comprise aseparator 12 fluidly coupled between the desalter 11 and the mixer 13.The desalter 11 removes metals and/or salts and other dissolvables fromcrude oil by combining crude oil and water to produce oil orhydrocarbon, brine, and a rag layer. The rag layer may be located on topof the brine, e.g., at the interface between the brine and thehydrocarbon, and/or entrained as droplets or masses within the brine.The rag layer comprises an emulsion of at least hydrocarbon, brine, andsolids and may also include other substances such as asphaltenes. Someor all of the rag layer emulsion and brine may be directed to theseparator 12, which may remove a significant portion of the brine. Therag layer emulsion may be passed to the mixer 13 from the desalter 11and/or the separator 12. In the mixer 13 one or more of additionalhydrocarbon, a demulsifier, a reverse demulsifier, a coagulant, and aflocculant may be mixed with the emulsion to produce a modified emulsionthat may be effectively filtered by the dead-end filter assembly 14. Themodified emulsion may be passed to a dead-end filter assembly 14 tofilter solids from the modified emulsion.

The components of the system 10 may be variously configured. Forexample, the desalter 11 may be configured in any of numerous ways. Thedesalter may take a variety of forms and shapes, including, for example,that of a tank, vessel, or receptacle, and may generally function as acoalescer, e.g., an electrostatic coalescer. The desalter may includeports for supplying substances to, and removing substances from, thedesalter, and these ports may be positioned at a variety of locations onthe desalter, e.g., on the top, bottom, or side of the desalter. Forexample, the desalter 11 may include one or more inlet ports 15, 16 forintroducing crude oil and water into the desalter 11 from a source 20 ofthe crude oil and a source 21 of water, respectively. Alternatively, thecrude oil and water may be combined upstream of the desalter andintroduced into the desalter via a single inlet port. A heater (notshown) may be associated with the desalter and/or sources of the crudeoil and water to heat the crude oil and water supplied to the desalter.The heater may be variously configured, including, for example, as aheat exchanger or a mechanism for injecting steam, e.g., directly intothe desalter. Various other chemicals, including, for example,demulsifiers and/or corrosion inhibitors, may be supplied to thedesalter via additional inlet ports or a common inlet port.

Within the desalter 11, the water washes metals and/or salts and otherdissolvables from the oil, forming brine. The denser coalesced brineseparates toward the lower region of the desalter 11 away from the lessdense hydrocarbon at the upper region of the desalter 11, and a raglayer may form on top of the brine and/or at the interface between thebrine and the hydrocarbon. The rag layer may also be entrained asdroplets or masses within the brine. The rag layer may comprise anemulsion of hydrocarbon, brine, and solids and may include othersubstances such as asphaltenes.

The desalter 11 may further include one or more outlet ports, e.g., anoutlet port 22 for discharging desalted oil or hydrocarbon and an outletport 23 for discharging some or all of the rag layer emulsion and thebrine. The outlet port 22 for discharging desalted hydrocarbon may bepositioned, for example, in the upper region of the desalter 11, and mayfluidly communicate with the desalted hydrocarbon within the desalter11. From the desalted hydrocarbon outlet port 22, the desaltedhydrocarbon may be directed to other components of the refinery systemfor further processing, including, for example, a fractionator. Theoutlet port 23 for discharging the rag layer emulsion and brine may bepositioned, for example, in the lower region of the desalter 11 and mayfluidly communicate with the brine and the rag layer emulsion within thedesalter 11. The discharged brine and rag layer emulsion may includevarying amounts of brine and rag layer emulsion, from mostly brine withsome of the rag layer emulsion to mostly rag layer emulsion with somebrine. For some embodiments, the desalter 11 may include an outlet port24 for discharging at least a portion of the rag layer emulsion. Thisoutlet port 24 may be positioned, for example, in the side of thedesalter 11, near the level of the rag layer emulsion, and may fluidlycommunicate with the rag layer emulsion within the desalter 11.

The separator 12 may also be configured in a variety of ways. For manyembodiments, the separator 12 may be configured as a bulk separator andmay have any of several shapes or forms including that of a tank,vessel, or receptacle. For example, the separator may comprise asettling tank, a gravity separator, or a plate separator such as acoalescing plate interceptor (CPI) separator. For many embodiments, theseparator 12 may comprise a plate separator available from PallCorporation of Port Washington, N.Y., USA under the trade designationLUCID.

The separator may be positioned at a variety of locations in the system.For example, the separator 12 may be positioned downstream of thedesalter 11 and upstream of the filter assembly 14, e.g., upstream ofthe mixer 13. The separator may include one or more inlet portspositioned at a variety of locations on the separator and may be coupledto the desalter either directly or indirectly via one or moreintervening components. For example, the separator 12 may include aninlet port 25 for receiving brine and the rag layer emulsion from thebrine/emulsion outlet port 23 of the desalter 11 via a brine/emulsionfeed line 26. Within the separator 11, a significant portion of thebrine may be separated from the rag layer emulsion. The separator mayalso include one or more outlet ports positioned at a variety oflocations on the separator. For example, an outlet port 27 fordischarging brine largely or substantially free of any emulsion may bepositioned in a lower region of the separator 12 and may fluidlycommunicate with the separated brine within the separator 12. The brinedischarged from the separator may be returned to the desalter and/ortreated to remove harmful substances before discharge or reuse. Theseparator 12 may further include an outlet port 28 fluidly communicatingwith the rag layer emulsion within the separator 12 and positioned,e.g., in an upper region of the separator 12, for discharging the raglayer emulsion with less brine. For some, but not all, embodiments thebrine depleted emulsion may comprise up to about 50% water or brine.

The mixer 13 may be configured in any of a wide variety of differentways and may take any of a variety of shapes and forms. For example, themixer may comprise an inline mixer or a mixing tank. Further, the mixermay be positioned in a variety of locations in the system. For example,the mixer may be positioned downstream of the desalter and upstream ofthe dead-end filter assembly. In the illustrated embodiment, the mixer13 may be positioned downstream of the desalter 11, downstream of theseparator 12, and upstream of the filter assembly 14. In addition, themixer may be fluidly coupled to one or more components of the system,either directly or indirectly via one or more other components. Forexample, the mixer 13 may be fluidly coupled to the separator 12, e.g.,directly coupled to the separator 12. For some embodiments, the mixer 13may, alternatively or additionally, be fluidly coupled directly to thedesalter 11.

The mixer may have one or more inlet ports positioned at a variety oflocations on the mixer. For example, the mixer 13 may include an inletport 29, e.g., on top of the mixer 13, for introducing the brinedepleted rag layer emulsion into the mixer 13, e.g., via abrine/emulsion feed line 30 extending between the brine/emulsion outletport 28 of the separator 12 and the brine/emulsion inlet port 29 of themixer 13. For some embodiments, the mixer 13 may alternatively oradditionally include an inlet port 31 positioned, e.g., on top of themixer 13, for introducing into the mixer 13 at least some of the raglayer emulsion directly from the desalter 11, for example, via a raglayer emulsion feed line 32 extending between a rag layer emulsionoutlet port 24 of the desalter 11 and the rag layer emulsion inlet port31 of the mixer 13.

To modify the rag layer emulsion and allow the emulsion to beeffectively filtered, one or more of additional hydrocarbon, ademulsifier, a reverse demulsifier, a coagulant, and a flocculant may beadded to the rag layer emulsion from the separator 12 and/or thedesalter 11. For example, the mixer 13 may include one or more inletports 33 positioned, e.g., in the upper region of the mixer 13, forintroducing the additional hydrocarbon from a source 34 of theadditional hydrocarbon, the demulsifier from a source 35 of thedemulsifier, the reverse demulsifier from a source 36 of the reversedemulsifier, the coagulant from a source 37 of the coagulant, and/or theflocculant from a source 38 of the flocculant. Alternatively, theadditional hydrocarbon, demulsifier, reverse demulsifier, coagulant,and/or flocculant may be added to the emulsion upstream from the mixer.Mixing the emulsion and one or more of the additional hydrocarbon, thedemulsifier, the reverse demulsifier, the coagulant, and the flocculantmay promote destabilization of the rag layer emulsion and at leastpartial, and even substantial, disintegration and decomposition of theemulsion and/or substances within the emulsion, facilitating removal andrecovery of the hydrocarbon bound up in the emulsion. For example, theadditional hydrocarbon may dissolve stabilizing agents, such asasphaltenes, in the emulsion. The additional hydrocarbon may also reducethe viscosity of the emulsion and/or establish the hydrocarbon as thecontinuous phase in the emulsion. The demulsifier may break downoil-in-water emulsions, while the reverse demulsifier may break downwater-in-oil emulsions. The coagulant and the flocculant may aggregateand agglomerate dispersed particles in the emulsion, forming largeraggregates that settle out of the emulsion. By mixing one or more of theadditional hydrocarbon, the demulsifier, the reverse demulsifier, thecoagulant, and the flocculant with the rag layer emulsion, the mixer 13may produce a modified emulsion including a substantially disintegrated,decomposed, and less emulsified mixture of hydrocarbon, brine, andsolids. For some, but not all, embodiments the modified emulsion maycomprise up to about 5% water or brine.

The mixer may have one or more outlet ports positioned at a variety oflocations on the mixer. For some embodiments, the mixer 13 may include arecirculation outlet port 40, e.g., in the lower region of the mixer 13,for discharging the modified emulsion to a recirculation pump 41 in arecirculation line 42. The recirculation pump 41 and recirculation line42 may recirculate the modified emulsion to a recirculation inlet port43, e.g., in the upper region, of the mixer 13, facilitating furtherdisintegration and decomposition of the rag layer emulsion within themixer 13. To further promote disintegration and decomposition of theemulsion within the mixer 13, a heater (not shown) may be associatedwith the mixer 13 or the recirculation line 42. For many embodiments,the heater may heat the emulsion to a temperature up to about 300° F. ormore. The mixer 13 may also include a modified emulsion outlet port 44,e.g., in the lower region of the mixer 13, for discharging the modifiedemulsion from the mixer 13 to the dead-end filter assembly 14, forexample, via a feed pump 48 in a modified emulsion feed line 45.

The dead-end filter assembly may be configured in any of numerous waysand may have any of several shapes or forms including that of a tank,vessel, or receptacle. For many embodiments, the filter assembly 14 mayinclude one or more filter elements 46, e.g., an array of several filterelements, contained within a housing 47. The housing 47 may include aninlet port 50 positioned, e.g., at one end region of the housing 47, forreceiving the modified emulsion and one or more outlet ports 51positioned, e.g., at an opposite end region of the housing 47, fordischarging the filtrate. The housing 47 may define a fluid flow pathbetween the inlet and outlet ports 50, 51 within the housing 47. One ormore filter elements 46, e.g., a plurality of filter elements 46, may bepositioned within the housing 47 across the fluid flow path, and thefilter elements 46 may be variously configured. For many embodimentseach filter element may have a hollow, generally cylindrical body whichincludes a permeable filter medium for removing solids from fluidsflowing inside-out or outside-in through the filter element. Any of awide variety of filter media may be included in the filter element,including permeable metallic, ceramic, or polymeric media. The filtermedia may be in the form of a pleated or spirally wound sheet or ahollow, cylindrical mass or sleeve and may be fashioned from a permeablemembrane, a fibrous or sintered sheet or mass, or a mesh sheet. Thefilter medium may have any of variety of filtering characteristics. Forexample, the filter medium may have a removal rating in the range fromabout 1 micron or less to about 100 microns or more. Each filter elementmay further include an end element, e.g., an end cap, on each axial endof the cylindrical body to direct fluid into or out of the hollowinterior of the filter element and generally radially through the filtermedium. For some embodiments, the dead-end filter assembly may comprisefilter elements having a polymeric fibrous filter medium available fromPall Corporation of Port Washington, N.Y. USA under the tradedesignation Profile AS.

The dead-end filter assembly may be positioned at a variety of locationsin the system. For example, the filter assembly 14 may be positioneddownstream of the desalter 11, downstream of the separator 12, and/ordownstream of the mixer 13. In the illustrated embodiment, the dead-endfilter assembly 14 may be fluidly coupled to the mixer 13. For example,the modified emulsion outlet port 43 of the mixer 13 may be coupled tothe modified emulsion inlet port 50 of the filter assembly 15, e.g., viathe modified emulsion feed line 45 and feed pump 48, to direct themodified emulsion into the dead-end filter assembly 15. Within thefilter assembly 15 the modified emulsion of hydrocarbon, brine, andsolids may be filtered by the filter elements 46, removing the solids,including colloids and undissolved asphaltenes. A substantial portion ofthe modified emulsion, including the hydrocarbon, brine, and dissolvedasphaltenes, passes through the filter medium as filtrate. The filtratemay be discharged from the filter assembly 15 via the filtrate outletport 51. From the filtrate outlet port the filtrate may be directed toany of numerous components. For example, the filtrate may be directed toa downstream separator for separating the filtered hydrocarbon from thebrine. In the illustrated embodiment, the filtrate may be recirculatedto the desalter 11, e.g., from the filtrate outlet port 51 of thedead-end filter assembly 15 to a filtrate inlet port 52 of the desalter11 via a filtrate recirculation line 53. Within the desalter 11, thefiltrate mixture of the hydrocarbon and brine, with the dissolvedasphaltenes, may separate into the hydrocarbon, which can be dischargedvia the desalted hydrocarbon outlet port 22, and brine, which can bedischarged via the brine/emulsion outlet port 23.

Embodiments of the invention further include numerous methods forprocessing crude oil. For example, methods for processing crude oil maycomprise adding water to crude oil to produce hydrocarbon and brine anda rag layer, the rag layer including an emulsion comprising hydrocarbonand brine and solids. The methods may further comprise modifying theemulsion, including adding one or more of additional hydrocarbon, ademulsifier, a reverse demulsifier, a coagulant, and a flocculant to theemulsion, and then directing the modified emulsion through a dead-endfilter assembly to remove the solids.

Water may be added to crude oil in a variety of ways. For example, watermay be added to the crude oil before the water and crude oil aresupplied to a desalter, or the water may be added to the crude oil inthe desalter. In the illustrated system 10, the oil and water may beintroduced into the desalter 11 separately, e.g., through separate inletports 15, 16. Alternatively, the crude oil and water may be suppliedsequentially or simultaneously to the desalter through a common inletport. Within the desalter, the water and crude oil combine, and thewater may remove metals and/or salts and other dissolvables from thecrude oil, forming brine. The nature of the crude oil, including thechemical composition of the crude oil itself and the amount and chemicalcomposition of the solids and other substances entrained and/ordissolved in the crude oil, may vary widely depending on many factors,including the geological source of the crude oil and the substancesadded to extract the crude oil from the geological source. Water may beadded to the crude oil in varying amounts sufficient to remove themetals and/or salts and other dissolvables. For example, water may beadded to the crude oil in an amount from about 3% water or less to about10% water or more by volume. Various other chemicals, including, forexample, demulsifiers and/or corrosion inhibitors, may be added to thecrude oil, the water, and/or the mixture of oil or hydrocarbon and water(brine) in the desalter to further treat the crude oil.

Adding water to the crude oil may also include pressurizing and/orheating the crude oil and/or water, for example, in the desalter. Formany embodiments, the hydrocarbon and brine may be heated in thedesalter to a temperature in the range from about 200° F. or less toabout 300° F. or more, e.g., in the range from about 225° F. to about275° F. The hydrocarbon and brine may be pressurized within the desalterto a pressure in the range from about 10 psig or less to about 200 psigor more. In some embodiments, the crude oil and/or water may not beheated or may not be pressurized.

Adding water to the crude oil may further comprise separatinghydrocarbon or oil from brine within the desalter and producing a raglayer. Separating the brine and the hydrocarbon may include coalescingbrine droplets in the desalter. For example, an electrical field may beapplied to the mixture of oil and brine in the desalter, the electricfield inducing a dipole in droplets of the brine and coalescing thebrine droplets. The denser coalesced brine droplets may then collect asan aqueous phase, e.g., in the lower region of the desalter, and theless dense desalted oil or hydrocarbon may collect substantially orlargely brine-free, e.g., in the upper region of the desalter. The raglayer may collect on top of the brine, e.g., at the interface betweenthe hydrocarbon and the brine, and/or may be entrained as small dropletsor masses, for example, in the brine. The rag layer may comprise any ofseveral substances, including an emulsion of oil, brine, and solids, aswell as asphaltenes. The composition of the rag layer emulsion may varydepending, for example, on the nature of the crude oil supplied to thedesalter. For example, some rag layer emulsions may comprisewater-in-oil emulsions, while other rag layer emulsions may compriseoil-in-water emulsions. Further, some rag layer emulsions may bechemically-stabilized by stabilizing agents such as asphaltenes, andsome rag layer emulsions may be particulate-stabilized by particulatesin the emulsion and may include little or no asphaltenes in theemulsion. One of many examples of a rag layer emulsion may compriseabout 30% to about 40% oil or hydrocarbon by weight, about 30% to about40% brine by weight, about 5% to about 20% solids by weight, and up toabout 10% asphaltenes by weight. These substances may be bound up withone another in the emulsion of the rag layer.

The desalted hydrocarbon and the brine comprising the rag layer emulsionmay be separately discharged from the desalter. The desalted hydrocarbonmay be discharged at a flow rate in the range from about 20,000 bbl/dayor less to about 100,000 bbl/day or more, where one barrel equals 42U.S. gallons (159 liters). The brine comprising the rag layer may bedischarged at a flow rate in the range from about 600 bbl/day or less toabout 6000 bbl/day or more. The desalted hydrocarbon may be dischargedfrom the desalter 11 via the desalted hydrocarbon outlet port 22 and maybe further processed, e.g., fractionated. The brine comprising the raglayer may be discharged from the desalter 11 via the brine/emulsionoutlet port 23. The brine and rag layer emulsion that are dischargedfrom the desalter 11 may include varying amounts of brine and emulsion,from mostly brine with the rag layer emulsion to mostly rag layeremulsion with some brine.

For some embodiments, methods for processing the crude oil may furthercomprise separating at least some of the brine from the brine and raglayer emulsion discharged from the desalter 11. For example, inembodiments where a significant amount of brine is removed from thedesalter 11 along with the rag layer emulsion, it may be beneficial tofurther separate some of the brine in a separator 12, e.g., a bulkseparator as previously described. The brine and rag layer emulsion may,for example, be discharged from the brine/emulsion outlet port 23 of thedesalter 11 and supplied to the brine/emulsion inlet port 25 of theseparator 12 via the brine/emulsion feed line 26. Within the separator12, at least some of the denser brine may separate from the less denserag layer emulsion in a variety of ways. For example, the brine maysettle from the rag layer emulsion in a settling zone, or the brine maydiverge from the rag layer emulsion along a plate separator. Separatingthe brine from the rag layer emulsion may also include separating largersolids from the rag layer. The larger solids, e.g., solids having aparticle size of about 20 microns or more, may settle into the brinefrom the emulsion, leaving the rag layer emulsion in the separator withfiner solids and less brine. The brine with or without larger solids maybe discharged from the separator 12, for example, via the brine outletport 27. The larger solids may then be removed, e.g., filtered, from thebrine, and some of the clean brine, e.g., up to about 50%, may bereturned to the desalter 11, while the reminder of the clean brine maybe treated and reused or discharged from the refinery system. Thebrine-depleted rag layer emulsion may be discharged from the separator12 and supplied to the mixer 13. For example, a brine depleted rag layeremulsion comprising up to about 50% water or brine by volume may bedischarged via the brine/emulsion outlet port 28 of the separator 12 andsupplied via the brine/emulsion feed line 30 to the brine/emulsion inletport 29 on the mixer 13. The flow rate into the mixer 13 from theseparator 12 may be in the range from about 6 bbl/day or less to about600 bbl/day or more.

In the illustrated embodiment, the rag layer emulsion may be supplied tothe mixer 13 from the desalter 11 after removing some of the brine inthe separator 12. In other embodiments, the rag layer emulsion, forexample, a rag layer emulsion with little brine, may additionally oralternatively be supplied to the mixer directly from the desalter. Forexample, the rag layer emulsion may be discharged from the rag layeremulsion outlet port 24 on the desalter 11 and supplied via the raglayer emulsion feed line 32 to a rag layer inlet port 31 of the mixer13.

Methods for processing crude oil may further comprise adding one or moreof additional hydrocarbon, a demulsifier, a reverse demulsifier, acoagulant, and a flocculant to the rag layer emulsion from the desalteror the separator to modify the emulsion and prepare the emulsion forfiltration. For example, any of a variety of hydrocarbons may be addedto dissolve substances, including asphaltenes, within the emulsion.Asphaltenes, which help to stabilize the emulsion, can quickly foul mostfilter media. The added hydrocarbon may dissolve the asphaltenes andother substances within the emulsion and enhance the decomposition ofthe emulsion, allowing the modified emulsion to be effectively filtered.The additional hydrocarbon may also reduce the viscosity of the raglayer emulsion, allowing the liquid components of the emulsion to movereadily pass through the filter elements, and may establish thehydrocarbon as the continuous phase of the emulsion. The addedhydrocarbon, which may be aromatic or nonaromatic, may include, forexample, one or more of reformate, naphtha, gas oil and hydrocarboncondensate. Any of a variety of demulsifiers and/or reverse demulsifiersmay be added to at least partially break down the emulsion and furtherfacilitate filtration of the emulsion. The added demulsifiers mayinclude, for example, one or more of ethoxylated or propoxylated acid-or base-catalyzed phenol-formaldehyde resins, ethoxylated orpropoxylated polyamines, ethoxylated or propoxylated di-epoxides, andethoxylated or propoxylated polyols. The added reverse demulsifiers mayinclude, for example, organic polymers, such as liquid cationicacrylamides. Any of numerous coagulants and/or flocculants may also beadded to aggregate and agglomerate solids in the emulsion, allowing thelarger agglomeration of solids to settle from the emulsion. Thecoagulant may include liquid inorganic or organic coagulating polymers,including, for example, a liquid, organic, water-soluble, low cationicquaternary ammonium polyelectrolyte. The flocculant may include, forexample, a liquid organic acrylic acid/acrylamide copolymer with a highmolecular weight and/or a low-to-medium anionic charge.

The amount of the additional hydrocarbon, demulsifiers, reversedemulsifiers, coagulants, and/or flocculants added to the rag layeremulsion from the desalter or separator may vary depending on a varietyof factors, including, for example, one or more of temperature;pressure; pH; amount of shear; composition of the organic and inorganicsolids; concentration of asphaltenes, well-treating chemicals,paraffins, or sulfur; API gravity of the crude oil, the difference indensity between the brine and the crude oil, and the composition andstability of the emulsion. For many embodiments, hydrocarbon may beadded to the emulsion in an amount up to about ten or more times thevolume of emulsion. For some embodiments, the amount of stabilizingagents, e.g., asphaltenes, in the rag layer emulsion may be small andless hydrocarbon may be added, e.g., one to two to more times the volumeof the emulsion. The demulsifier, reverse demulsifier, coagulant, and/orflocculant may be added in an amount in the range from 0% to about 1% ormore of the rag layer.

The additional hydrocarbon, deemulsifier, reverse demulsifier,coagulant, and flocculant may be added to the rag layer emulsion fromthe desalter or the separator in any of a variety of different ways. Formany embodiments, the additional hydrocarbon, deemulsifier, reversedemulsifier, coagulant, and/or flocculant may be added to the rag layeremulsion within the mixer 13. Within the mixer one or more of theadditional hydrocarbon, demulsifier, reverse demulsifier, coagulant, andflocculant are mixed with the rag layer emulsion to produce a modifiedemulsion that is sufficiently broken down into its constituents,including hydrocarbon, brine, solids, and dissolved asphaltenes to allowthe solids to be effectively filtered from the hydrocarbon and brine.Mixing one or more of the additional hydrocarbon, demulsifier, reversedemulsifier, coagulant, and flocculant with the rag layer emulsion maythen comprise substantially dissolving one or more substances, includingasphaltenes, from the rag layer emulsion and/or destabilizing ordecomposing the rag layer emulsion. For example, a modified emulsioncomprising up to about 5% water by volume may be discharged from themodified emulsion outlet port.

For many embodiments, mixing one or more of the additional hydrocarbon,deemulsifier, reverse demulsifier, coagulant, and flocculant with therag layer emulsion may further comprise recirculating the modifiedemulsion through the mixer. For example, the modified emulsion may bedischarged from the mixer 13 via the recirculation outlet port 40 andrecirculated through the mixer 13 via the recirculation pump 41 in therecirculation line 42, reentering the mixer 13 at the recirculationinlet port 38. Recirculating the modified emulsion allows asphaltenesand other substances to be even more completely dissolved and even morethoroughly destabilizes and decomposes the emulsion, facilitating therecovery of an even greater amount of the hydrocarbon in the emulsion.

Heating the emulsion may further promote dissolving substances such asasphaltenes and destabilizing and decomposing the emulsion. The emulsionmay be heated to a temperature in a range up to about 300° F. or more,for example, in the mixer 13, in the recirculation line 42, or en routeto the dead-end filter assembly 14.

After mixing, the modified emulsion may be directed through a dead-endfilter assembly to remove solids and produce a filtrate principallycomprising filtered hydrocarbon and brine. The modified emulsion may bedischarged from the mixer and supplied to the dead-end filter assemblyeither directly or indirectly via one or more additional components. Forexample, in the illustrated embodiment, the modified emulsion may bedischarged from the mixer 13 via the modified emulsion outlet port 44and supplied to the dead-end filter assembly 14 via a feed pump 48 inthe modified emulsion feed line 45, entering the dead-end filterassembly 14 via the modified emulsion inlet port 50. The modifiedemulsion may be supplied to the dead-end filter assembly at a variety offlow rates and pressures, depending, for example, on the size of thedead-end filter assembly and the amount of the modified emulsion to beprocessed. For some embodiments, the flow rate of the modified emulsioninto the dead-end filter assembly may be in the range from about 12bbl/day gpm or less to about 6000 bbl/day gpm or more. The pressure maybe in the range from about 10 psig or less to about 200 psig or more.

Within the dead-end filter assembly 14, all of the modified emulsionpasses through one or more filter elements 46. Passing the modifiedemulsion through the filter elements 46 includes directing all of themodified emulsion through the filter media of the filter elements 46,where at least a substantial portion of the solids are removed. For manyembodiments, directing the modified emulsion through the filter mediummay include directing the modified emulsion through a filter mediumhaving a removal rating in the range from about 1 micron or less toabout 100 microns or more, e.g., from about 1 micron or less to about 40microns. Filtered hydrocarbon and brine, as well as dissolvedasphaltenes, may then emerge as filtrate from the filter elements 46 andmay be directed by the housing 47 to the filtrate outlet port 51. Thefiltrate may be discharged from the dead-end filter assembly to avariety of components for further processing. For example, the filtratemay be discharged to a separator to separate the filtered hydrocarbonfrom the filtered brine. The filtered hydrocarbon may then be furtherprocessed, e.g., fractionated, within the refinery system. In theillustrated embodiment, the filtered hydrocarbon and brine may berecirculated to the desalter. For example, filtrate, including both thefiltered hydrocarbon and brine, and any dissolved asphaltenes, may bedischarged from the filtrate outlet port 51 of the dead-end filterassembly 14 and returned to the desalter 11 via the filtraterecirculation line 53, entering the desalter 11 via one of the inletports, e.g., the filtrate inlet port 52. Within the desalter 11, thefiltered hydrocarbon and brine and any dissolved asphaltenes combinewith the crude oil and water in the desalter 11, where they may beginthe process of breaking down the rag layer emulsion and dissolvingsubstances, including asphaltenes, in the rag layer emulsion. Thefiltered hydrocarbon and brine may separate within the desalter 11 andmay be respectively discharged from the desalter 11 along with thedesalted hydrocarbon and the brine, e.g., via the desalted hydrocarbonoutlet port 22 and the brine/emulsion outlet port 23.

Methods embodying the invention may further comprise cleaning and/orreplacing the filter elements in the dead-end filter assembly after thefilter elements become sufficiently fouled to require cleaning orreplacing. For example, after the pressure drop across the filterelements 46 rises to a predetermined level, or the flow rate through thefilter elements 46 falls to a predetermined level, flow of the modifiedemulsion through the dead-end filter assembly 14 may be terminated. Thefilter elements 46 may then be cleaned in any of numerous ways. Forexample, the filter elements may be cleaned in situ, i.e., within thefilter housing, or ex situ, i.e., outside the filter housing, using avariety of solvent soaking techniques, including hot hydrocarbonsoaking, and/or washing or backwashing techniques, with or without gasassist. Alternatively, the fouled filter elements 46 may be replacedwith new filter elements 46. Flow of the modified emulsion may then bereestablished through the dead-end filter assembly 14.

Although the invention has been disclosed in the embodiments previouslydescribed and/or illustrated, the invention is not limited to thoseembodiments. For instance, one or more features of an embodiment may beeliminated or modified, one or more features of one embodiment may becombined with one or more features of other embodiments, or embodimentswith very different features may be envisioned, all without departingfrom the scope of the invention. For example, the separator 12 may beeliminated from the system 10 of FIG. 1, the remainder of the systemincluding the previously described components operating as previouslydescribed. The rag layer emulsion may be discharged from the rag layeremulsion outlet port 24 of the desalter 11 and supplied directly orindirectly to the mixer 13, e.g., via the rag layer emulsion feed line35. Brine with little or no rag layer emulsion may be removed from thedesalter 11, e.g., via the brine/emulsion outlet port 23, treated, andthen reused within the refinery system or discharged from the refinerysystem.

As another example, a system for processing crude oil may include amodified dead-end filter assembly 14, for example, as shown in FIG. 2.The remainder of the system may include the previously describedcomponents operating as previously described. The modified dead-endfilter assembly 14 may include a settling zone 54 within the housing 47downstream of the filter elements 46. Within the settling zone 54, theless dense filtered hydrocarbon, along with other substances such as thedissolved asphaltenes, may separate, e.g., toward the upper region ofthe housing 47, away from the denser filtered brine, e.g., in the lowerregion of the housing 47. The housing 47 may further include a brinetrap 55 in the lower region of the housing 47 to collect the brine. Afiltered hydrocarbon outlet port 56 for discharging the separatedfiltered hydrocarbon, along with the dissolved asphaltenes, may bepositioned on the housing 47, e.g., in the upper region, and a filteredbrine outlet port 57 for discharging filtered brine may also bepositioned on the housing 47, e.g., in the brine trap 55. All or aportion of the discharged filtered brine may be sent to the desalter orany other component of the refinery system or may be treated anddischarged from the refinery system. All or a portion of the dischargedfiltered hydrocarbon may be returned to the desalter, e.g., via thefiltrate recirculation line 53, or may be directed to other componentsof the refinery system for further processing, e.g., fractionation.

As an alternative, the system 10 of FIG. 1 may further include aseparator (not shown) downstream of the dead-end filter assembly 14. Thefiltrate from the dead-end filter assembly 14, including the filteredhydrocarbon, the filtered brine, and any dissolved asphaltenes, may bedischarged from the filtrate outlet port 51 and passed, directly orindirectly, to the separator, where the filtered hydrocarbon may beseparated from the filtered brine within the separator. The separatormay comprise a bulk separator as previously described or any otherseparator suitable for separating the filtered hydrocarbon from thefiltered brine. The filtered hydrocarbon may be discharged from theseparator and sent to the desalter or any other component of therefinery system. The filtered brine may be discharged from the separatorand sent to the desalter or any other component of the refinery systemor treated and discharged from the refinery system.

Methods for processing crude oil may further comprise separating thefiltrate from the dead-end filter assembly into filtered hydrocarbon,along with other substances such as the dissolved asphaltenes, andfiltered brine, e.g., within the dead-end filter assembly or within aseparator. For example, in the illustrated embodiment separating thefiltrate may include passing the filtrate into a settling zone 54 in thehousing 47 of the dead-end filter assembly 14 downstream of the filterelements 46. In the settling zone 54, the denser filtered brine maysettle in a lower region of the housing 47, e.g., into the brine trap55, away from the less dense filtered hydrocarbon in an upper region ofthe housing 47. Methods may further comprise separately dischargingfiltered hydrocarbon and the filtered brine from the dead-end filterassembly 15, e.g., via the filtered hydrocarbon outlet port 56 and thefiltered brine outlet port 57, respectively, as previously described.

Another embodiment of a system for processing crude oil may furthercomprise a coalescer assembly 60, for example, as shown in FIG. 3. Theremainder of the system may include the previously described componentsoperating as previously described. The coalescer assembly may be fluidlycoupled, directly or indirectly, to a dead-end filter assembly, forexample, to the filtered hydrocarbon outlet port 56 of the dead-endfilter assembly 14 of the system of FIG. 2 or to the filtrate outletport 51 of the dead-end filter assembly 14 of the system 10 of FIG. 1.In both systems, the coalescer assembly may serve to break any remainingemulsion and/or to coalescer the filtered brine, including any smalldroplets of filtered brine, as the discontinuous phase, entrained in thefiltered hydrocarbon, as the continuous phase. The coalesced filteredbrine and the filtered hydrocarbon may then be separated from oneanother, for example, in the coalescer assembly 60.

Any of numerous coalescer assemblies may be employed. Generally, thecoalescer assembly 60 may include a housing 61, e.g., a tank, a vessel,or any other receptacle. The housing 61 may have an inlet port 62positioned, e.g., at one end of the housing 61, and one or more outletports. For example, in the illustrated embodiment, the housing 61 mayinclude a hydrocarbon outlet port 63 positioned, e.g., at the oppositeend in an upper region of the housing 61, and a brine outlet port 64positioned, e.g., at the opposite end in a lower region of the housing61. The housing 61 may include a brine trap 65 for collecting the brine,and the brine outlet port 64 may be located on the brine trap 65.

The coalescer housing 61 defines a fluid flow path within the housing 61between the inlet port 62 and the outlet ports 63, 64. One or morecoalescer elements 66, e.g., a plurality of coalescer elements 66, maybe positioned within the housing 61 across the fluid flow path. Eachcoalescer element 66 may be variously configured. For many embodiments,each coalescer element may have a hollow, generally cylindrical bodywhich includes a permeable arrangement for coalescing small filteredbrine droplets, as the discontinuous phase, entrained in the filteredhydrocarbon, as the continuous phase. Each coalescer element may furtherinclude end elements, e.g., an end cap, on each axial end of thecylindrical body to direct fluid into or out of the hollow interior ofthe coalescer element and generally radially through the coalescingarrangement. For some embodiments, the coalescing assembly may comprisecoalescing elements available from Pall Corporation of Port Washington,N.Y. USA under the trade designation PhaseSep.

The coalescer assembly 60 may further include a separating regiondownstream of the coalescer elements 66 for separating the coalescedfiltered brine from the filtered hydrocarbon. The separating region maybe variously configured. For example, the separating region may includea permeable separation medium which allows passage of one of thecomponents, e.g., the filtered hydrocarbon, but retards passage of theother component, e.g., the filtered brine. The hydrocarbon outlet portmay then fluidly communicate with one side, e.g., the downstream side,of the permeable separation medium, while the brine outlet port fluidlycommunicates with the other side, e.g., the upstream side, of theseparation medium. In the illustrated embodiment, the separating regionmay comprise a settling zone 67 within the housing 61 downstream of thecoalescer elements 66. Within the settling zone 67, the less densefiltered hydrocarbon, along with other substances such as the dissolvedasphaltenes, may separate, e.g., toward the upper region of the housing61, away from the denser coalesced and filtered brine, e.g., in thelower region of the housing 61. The coalesced, filtered brine may bedischarged from the coalescer assembly 60, e.g., via the brine outletport 64, and sent to the desalter or any other component of the refinerysystem or may be treated and discharged from the refinery system. Thefiltered hydrocarbon may have less than about 25 ppmw free water and maybe discharged from the coalescer assembly 60, e.g., via the hydrocarbonoutlet port 63. From the coalescer assembly 60, some or all of thedischarged hydrocarbon may be sent to the desalter 11 or to the mixer13. Returning some or all of the discharged hydrocarbon to the mixer 13allows reuse of the hydrocarbon, reduces the volume of fresh additionalhydrocarbon to be added to the mixer 13, and helps establish thehydrocarbon as the continuous phase in the modified emulsion. For manyembodiments, the coalescer assembly 60 may so effectively break anyoil/brine emulsion that the hydrocarbon may be directly sent to anyother component of the refinery system, e.g., a fractionator, forfurther processing.

Methods for processing crude oil may further comprise coalescingfiltered brine, including any small droplets of filtered brine, as thediscontinuous phase, entrained in the filtered hydrocarbon, as thecontinuous phase, along with any dissolved asphaltenes, and thenseparating the coalesced, filtered brine from the filtered hydrocarbon.Coalescing the filtered brine may include directing the filteredhydrocarbon and brine through one or more coalescer elements 66 within acoalescer assembly 60, including aggregating small droplets of filteredbrine and producing larger droplets or masses of filtered brine.Separating the coalesced, filtered brine filtered hydrocarbon may, forexample, include settling the denser coalesced brine away from the lessdense filtered hydrocarbon in a settling zone 67. Alternatively,separating the brine from the hydrocarbon may comprise passing one butnot the other of the brine and hydrocarbon through a permeableseparation medium. Methods may further comprise separately dischargingthe filtered hydrocarbon and the filtered brine from the coalescerassembly 60, e.g., via the hydrocarbon outlet port 63, and the brineoutlet port 64, respectively, as previously described. Discharging thefiltered hydrocarbon from the coalescer assembly 60 may includereturning some or all of the filtered hydrocarbon to the desalter 11 orthe mixer 13 or sending the filtered hydrocarbon to any other componentof the refinery system.

Another embodiment of a system for processing crude oil may comprise amagnetic filter 70, for example, as shown in FIG. 4. The remainder ofthe system may include the previously described components of FIGS. 1, 2and/or 3 operating as previously described. The magnetic filter mayserve to remove magnetic solids, e.g., magnetic particles, and may bepositioned at a variety of locations in the system, including downstreamof the desalter, downstream of the separator, and/or downstream of themixer. In the illustrated embodiment, the magnetic filter 70 may bepositioned upstream of the mixer 13 to remove magnetic solids from theemulsion entering the mixer 13 and inhibit fouling of mixer 13.Alternatively or additionally, a magnetic filter may be located in therecirculation line of the mixer or between the mixer and the dead-endfilter assembly to remove magnetic solids from the modified emulsion.

Any of a wide variety of magnetic filters may be employed. Generally,the magnetic filter 70 may include a housing 71 having the shape, forexample, of a tank, vessel, or any other receptacle. The housing 71 mayinclude a fluid inlet port 72 and a fluid outlet port 73 and may definea fluid flow path between the inlet and outlet ports 72, 73. In thefluid flow path within the housing 71, one or more magnetic elements 74may be arranged to attract and remove magnetic solids from the emulsion,e.g., the rag layer emulsion or the modified emulsion, flowing along thefluid flow path in the magnetic filter 70. In the illustratedembodiment, the fluid inlet port 72 of the magnetic filter 70 may befluidly coupled, directly or indirectly via one or more othercomponents, to the brine/emulsion outlet port 28 of the separator 12,e.g., via a first portion 30A of the brine/emulsion feed line. The fluidoutlet port 73 of the magnetic filter 70 may be fluidly coupled,directly or indirectly, to the brine/emulsion inlet port 29 of the mixer13, e.g., via a second portion 30B of the brine/emulsion feed line. Therag layer emulsion may thus be directed through the magnetic filter 70to remove magnetic solids as the emulsion is passed between theseparator 12 and the mixer 13.

Methods for processing crude oil may further comprise magneticallyremoving solids from the emulsion, e.g., either the rag layer emulsionor the modified emulsion. Magnetically removing the solids may comprisedirecting the emulsion through a magnetic filter, including passing theemulsion past magnetic elements that attract and remove magnetic solidsfrom the emulsion. In the illustrated embodiment, directing the emulsionthrough the magnetic filter 70 may include passing the rag layeremulsion from the brine/emulsion outlet port 28 of the separator 12 intothe fluid inlet port 72 of the magnetic filter 70, along the magneticelements 74 where the magnetic solids are removed, and from the fluidoutlet port 73 of the magnetic filter 70 to the brine/emulsion inletport 29 on the mixer 13. In other embodiments, directing the emulsionthrough the magnetic filter may include passing the modified emulsionthrough a magnetic filter located in the recirculation line of the mixeror located between the mixer and the dead-end filter assembly.

Other embodiments of the system may include other components, such asone or more additional separators, located elsewhere in the system. Forexample, the mixer may comprise a static inline mixer which may bedirectly coupled to a separator for separating additional brine and/orsolids from the modified emulsion before the modified emulsion is fed tothe dead-end filter assembly.

In still other embodiments, the rag layer emulsion may be stored, e.g.,in tanks or other receptacles. The one or more of the additionalhydrocarbon, demulsifier, reverse demulsifier, coagulant, and flocculantmay be added to the rag layer emulsion either before or after storage.For example, the rag layer emulsion may be directed from the rag layeremulsion outlet port of the desalter or the brine/emulsion outlet portof the separator to a storage tank, where the rag layer emulsion may bestored for a period of time. From the storage tank, the rag layeremulsion may later be supplied, directly or indirectly via othercomponents of the system, to the mixer. The rag layer emulsion may thenbe modified and filtered as previously described.

The present invention thus encompasses innumerable embodiments and isnot restricted to the particular embodiments that have been described,illustrated, and/or suggested herein. Rather, the present inventionincludes all embodiments and modifications that may fall within thescope of the claims.

The use of the terms “a” and “an” and “the” and “at least one” andsimilar referents in the context of describing the invention (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. The use of the term “at least one”followed by a list of one or more items (for example, “at least one of Aand B”) is to be construed to mean one item selected from the listeditems (A or B) or any combination of two or more of the listed items (Aand B), unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having.” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as” and“e.g.”) provided herein, is intended merely to better illuminate theinvention and does not pose a limitation on the scope of the inventionunless otherwise claimed. No language in the specification should beconstrued as indicating any non-claimed element as essential to thepractice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A method for processing crude oil comprising: adding water to crudeoil to produce hydrocarbon and brine and a rag layer including anemulsion comprising hydrocarbon and brine and solids; modifying theemulsion, including adding one or more of additional hydrocarbon, ademulsifier, a reverse demulsifier, a coagulant, and a flocculant to theemulsion; and directing the modified emulsion through a dead-end filterassembly to remove solids.
 2. The method of claim 1, further comprisingseparating a portion of the brine from the emulsion before modifying theemulsion.
 3. The method of claim 1, wherein adding water to the crudeoil includes passing crude oil and water into a desalter, the methodfurther comprising recirculating filtrate from the filter assembly tothe desalter.
 4. The method of claim 1, further comprising directingfiltrate from the filter assembly to a coalescer assembly and separatelyextracting filtered hydrocarbon and brine from the coalescer assembly.5. The method of claim 4, when the filtrate includes filteredhydrocarbon and brine, the method further comprising separating aportion of the brine from the filtered hydrocarbon and directing thefiltered hydrocarbon to the coalescer assembly.
 6. The method of claim 1wherein adding one or more of additional hydrocarbon, a demulsifier, areverse demulsifier, a coagulant, and a flocculant includes mixing theadditional hydrocarbon, demulsifier, reverse demulsifier, coagulant,and/or flocculant with the emulsion.
 7. The method of claim 1 furthercomprising directing the emulsion or the modified emulsion through amagnetic filter before directing the modified emulsion through thefilter assembly.
 8. A system for processing crude oil, the systemcomprising: a desalter including one or more inlets for introducingcrude oil and water into the desalter, the desalter producinghydrocarbon and brine and a rag layer including an emulsion comprisinghydrocarbon and brine and solids, the desalter further including a firstoutlet for discharging at least a portion of the hydrocarbon and one ormore additional outlets for discharging brine and the emulsion; a mixercoupled to the desalter to modify the emulsion including adding one ormore of additional hydrocarbon, a demulsifier, a reverse demulsifier, acoagulant, and a flocculant to the emulsion; and a dead-end filterassembly coupled to the mixer to filter solids from the modifiedemulsion.
 9. The system of claim 8, further comprising a separatorcoupled to the desalter to separate at least a portion of the brine fromthe discharged emulsion, wherein the mixer is coupled to the separator.10. The system of claim 8, wherein the filter assembly includes afiltrate outlet coupled to an inlet of the desalter.
 11. The system ofclaim 8, further comprising a coalescer assembly coupled to the dead-endfilter assembly to separate filtrate from the filter assembly intofiltered hydrocarbon and brine.
 12. The system of claim 8 wherein thedead-end filter assembly includes a settling region for separating atleast a portion of the filtered brine from the filtrate, the filterassembly including an outlet for the brine-depleted filtrate coupled tothe coalescer assembly.
 13. The system of claim 8 further comprising amagnetic filter positioned upstream of the dead-end filter assembly toremove magnetic solids.